电脑电源线插头热固性嵌件注塑工艺及模具设计（全套含CAD图纸）
收藏
资源目录
压缩包内文档预览：(预览前20页/共22页)
编号：1953516
类型：共享资源
大小：2.17MB
格式：ZIP
上传时间：2017-10-22
上传人：机****料
认证信息
个人认证
高**（实名认证）
河南
IP属地：河南
50
积分
- 关 键 词：
-
电脑
电源线
插头
热固性
注塑
工艺
模具设计
全套
cad
图纸
- 资源描述：
-
- 内容简介：
-
在印刷注射模工具中的热力情况 R. A. 哈里斯*, R. J. M. 海牙 & P. M. 狄更斯快速制造的研究小组 沃尔福森技工学校 & 制造工程 拉夫堡大学, 英国 * 通讯作者: R.A.Harrislboro.ac.uk 1.摘要使用立体光刻(SL)作为一种快速模具技术提供了一个低成本的注塑模具及快速选择方法努力生产少量的零件。然而,先前的工作已经证明,不同的特点是由水晶塑料件生产模具和生产树脂与传统加工方法。不同地区特点意味着并不是真正的问题相同由硬加工和突出的弱点SL工具。这种差异是由于冷却速度所经历的一部分。SL模具零件产生冷却速度低于那些来自金属工具结果不同的导热模具材料本身。这项工作的程度有关建立传热特性差异。也证明了不同冷却速率实时数据采集。结果阐述了热史上非常不同的塑造传授可能会导致不同的特色部分。阐述了如何工作经验的热力学条件立体光刻模具可用于一个优势。一个实例详细介绍了模具的使用为注塑树脂的polyether-ether-ketone(聚醚醚酮)具有较高的工艺参数的要求。结果实例表明,不仅是快速加工方法立体光刻能够生产一个低流量的聚醚醚酮的一般部分,而且在条件不可能使用金属模具。立体光刻模具的热特性允许部件完全水晶聚醚醚酮生产的模具在室温,相当于一个钢模具需要200 C温度和更高的注射压力和速度。关键词:立体光刻、快速模具、注塑、传热、聚醚醚酮。2.背景术语快速成型(RP)指的是生产物理几何的一群过程。RP工艺直接产生一个几何资料来源于一个三维代表(如下。CAD -计算机辅助设计。的过程产生的几何特征的添加剂,逐层制造顺序,当启动运行于不顾。立体光刻(SL)就是这样的一个RP的过程。 SL是最成熟的商业记者的过程,它的发展始于1980年代中期。SL代表一个最几何精确的商业记者推动最小特徵尺寸大约0.1毫米的可能。SL生成一个实心物体选择性的固化树脂感光液暴露于紫外光雷射所提供。 部分产生部分-次要-部分在一个平台,包含在浴缸里的液体树脂。材料可用于过程被限制为丙烯酸和环氧树脂。树脂可具有不同的特征,但他们都是本质上的基因型的环氧树脂和丙烯酸(在这件作品中,环氧树脂采用)。 结果表明SL可产生模具腔,可以用于注塑有限数量的部分在各种聚合物(1、2、3、4、5、6、7)。(插入)模具腔产生的具有非常不同的树脂传热特性相比,注塑模具材料的传统。导热系数 SL 环氧基树脂0.2W/m-K钢铁50W/m-K铝200W/m-K这些不同的传热性能通常被看作是一个虚弱的SL成型过程,其结果较慢的冷却时间,因此部分生产周期时间。它也显示了传热性能的模具零件,SL结果表明不同的特点,由金属制成的模具。结晶聚合物已经证实可展现出以下生产环氧树脂的特点,从模具相比,金属模具。 更大的强度和刚度(8) 较低的冲击强度(9) 更大的密度(10)更大的收缩(11)这种差异涉及到一个更高的层次所开发的结晶度SL模具零件内由于其较慢的速率。这是由于慢的速率的不同的热导率的模具材料。这项工作在速率的差异,说明了部分模具冷却在SL和铝由一个实时数据采集调教。热条件优势SL模具加工经验后展现在了相应的案例研究。 3.研究方法 3.1 工具设计 部分和工具设计实验中使用来自早期工作的一部分收缩的评价。由一个标本的模压棒材形状与尺寸12.7毫米,直径为127毫米,墙的厚度为3.2毫米。这一端封闭腔,测量6.4毫米,宽3.2毫米和深度。门是一个开放的地区使用,确保没有的热量和压力积累,SL模具很容易。 一个工具不纳入弹射系统以确保一个奇异的传热速度在模腔,即包括钢弹射销环氧模具可以提供一个范围内的模具,通过举办热在一个更大的速度。没有一个弹射系统没有问题,部分被拆装方便的手。 评估工具材料是铝环氧树脂。铝被选为制造金属模具材料比较合适,因为它是经常使用在生产金属工具在很短的时间(快速加工利率可能)。铝(铝)也代表了一种工具高对比的传热特性相比,环氧树脂。 3.2 注塑法 聚合物应用于注塑是尼龙PA66,特别是Bergamid A70NAT PolyOne产生的。 这是干前迅速成型。注射成型机使用了一条巴顿菲尔 600/125模型Unilog 4000年疾病控制和预防中心控制单元。这台机器由一个60吨液压夹紧装置和一个125 x35mm往复螺杆注射单位。 注塑参数的定义:注射速度使用是100毫米/秒。喷射压力是150酒吧。在后续充型压力为150酒吧是举办了1.5秒。一个23.5C模具温度、注射温度记录之前。一个温度为270C的融化。编码的冷却时间40秒。 3.3 温度感测为了建立传热特性发生在每一种模具温度记录是整个成型周期由聚四氟乙烯绝缘k的流动与焊接热电偶的小费。这是在三个位置插入热电偶在模腔。两人沿着其长度分布均匀的侧面和一个移动的中心移动侧链长度对模具。这些职位是说明图1。热电偶的顶端,它坐落于0.5毫米表面下的成型的脸。热电偶是插入,从后方的模具插入通过钻孔约1毫米。终点这个洞被用了相似的球嗅刀具姿态以焊接顶端的热电偶。这是为了确保一个好的联系两个平面之间不需要任何粘合剂。认为使用任何粘合剂可以建立不确由于温度记录值的压敏胶粘接剂制造没有相同的传热特点为模具材料。热电偶牢牢插入进洞里,用胶水粘在保证电线长度使录音来被破坏,没有任何信号由于振动从注射成型机。调解书的热电偶的洞里插了图2。温度记录系统的校准工具以便核实记录值热电偶是准确的反映了温度条件在模腔表面。在插入之后在模具、一个已知的温度是应用于每一个探测器的位置上模腔表面和比较,从每一个记录温度探测器和实际模腔表面温度是在尊重他们的同时价值观及其响应温度的变化。在这两种情况下(SL和铝模具)之间的差额热电偶温度测量和实际地面温度不会超过+ / - 1度。温度剖面的经验所获得的每一个模具设置,数据采集监测和记录的温度需要一段时间。阅读资料来自三个热电偶在每一个模具,这些阅读资料被转换成数字信号,用一个发达的软件程序,然后过滤和采样时间间隔,以提供一个线性温度历史剖面的成型条件。这个组织方面的经验记录了气温型材生产过程中模具在一百一十分钟一个时期。二十线脚条制造和温度剖面记录。 4.结果和议论 4.1 温度剖面在一次机会 在一次温度剖面的例子所经历的热型材模具铝、树脂中显示图3及图4。以下的观察可以由热历史概况:每个温度剖面显示温度一致开始 23.5度。温度环境处于注塑机18度。更大的环境温度的模具是由于关闭的橱柜组合(完全封闭的安全向导)和热从机器的液压夹紧单元中时油保持在一个恒定的温度。严密观察最高温度下在每个案例表明,所经历的温度略高于靠近门了,材料的进入模具。这可能是由于他们稍长时间的暴露在炎热的聚合物熔体由于方式模具填充。显示出一个铁道模具温度骤降峰值后,在48-52秒。这是开模时的热在模具另一条路再突然发现自己进入空气。没有这样的特征就是显示在铝模具温度山峰只有2.8秒之后,几乎所有的活动已经停止48-52秒。 4.2 超过20次平均温度剖面热史的相似性剖面从每个射击(不超过+ / - 5%)平均气温资料,允许每个模具产生的类型(铝和SL)。经验丰富的平均温度分布在每一个模具类型超过20个投篮被显示在图5。 图5显示出这说明了截然不同的温度条件在经历了SL和铝等模具。温度在铝合金模具活动发生在很短的时间内由于高导热系数的材料。内部的温度场分布在SL了模具极端得多,拖延,外在的帮助(即由压缩空气冷却)SL模具将15分钟回到它的环境温度。 5.案例研究 5.1 背景这项工作进行了描述作为欧盟资助项目信息管理系统(IMS可。参与项目部分研究使用的Stereolithography(SL)模具生产原型大批塑料件注射成型。该项目已经成功地塑造不同的聚合物在SL模具有序发展这代表着它们的难度。这些聚合物在顺序是聚丙烯、丙烯腈-丁二烯-苯乙烯、尼龙66、尼龙66有30%的玻璃的内容。使用polyether-ether-ketone(聚醚醚酮)将是一个重要的“跳”的进展到一个高度mould-aggressive材料。 聚醚醚酮是一种高水晶工程聚合物的温度电阻、高硬度、精度高、环境稳定性和较低的摩擦性能。它是用来在高端塑料的应用,如在医疗和航空航天工业。聚醚醚酮也有极端的注塑加工要求;熔融温度为400C,有大约200模具温度和一个典型的喷射压力C大约800吧。这个特定的部分之间进行了快速制造一起研究小组(RMRG)的Loughborough大学和全球塑料处理器,Ensinger在德国。 5.2 第一次尝试第一次尝试在聚醚醚酮树脂成型模具中使用一个简单的模具的几何学,它已经被用于由作者先前的实验中(12、13)。模具,包括直接浇口模具围绕一个中心圆柱核心特征,后面跟着一个法兰顶出针上行动。一个横截面的模具如图6。其中两个成功投产15聚醚醚酮树脂模具零件彼此。在一个合理的模具成型后的状态,尽管他们展出的角度穿在进入SL模具材料。使用的工艺参数如下图所示: 用于1st工艺参数的试验 聚合物熔体模具注射 注射速度 温度 (oC) 温度 (oC) 压力(bar)(mm/sec)SL 模具 40023 (room temp) 25 7 400 200 500 50等效要求钢模 部分显示非常有趣的特性。自己部分地区在与SL模具是灰的,这表明该地区的一部分是水晶体。地区与钢直浇布什和顶出针是棕色的,这表明一种无定形的部分地区。这是说明图7。 5.3 第二次尝试麻省理工学院开放式课件可使用真正的零部件设计项目作为一个示范的技术转让。提供一个叶轮工业的合作伙伴Rotax-Bombardier已经产生了各种注塑模具。用树脂聚合物在最初的成功1st我们决定尝试试验应该产生这些叶轮零件在聚醚醚酮。两个SL模具零件成功制造出10偷看彼此。遭受穿在模具的第一点资料进入模具、也在4点资料进入腔。 用于2nd工艺参数的试验 聚合物熔体模具注射注射速度 温度 (oC) 温度(oC) 压力 (bar)(mm/sec)SL 模具 400 23 (room temp)3010 400 200 65070等效要求钢模 显示部分地区又非晶态聚合物接触到钢领域的模腔。这些零件在图8。 6.讨论结果表明,该方法具有良好的热特性强加于SL模具,这些文件通常被看作是一种劣势的过程中,可能在某些情况下,并允许成型有利条件不可能在金属工具。成功的方法及其特点,部分是由于模具的热性能。伟大的差异量化的热力学条件已经做的实验经验。SL的环氧模具把热能远离部分远远低于钢模具是因为他们不同的热导率。这使得一个不能供热的模具和较低的工艺参数能够被使用。这项工作阐述了固有的传热特性,使他们SL模具注塑应用使用,SL成型将无法承受预热和更高注射压力和速度的要求,在等效金属工具。 特别有趣的是保证非晶态聚合物的地方展示进来接触热传导高的区域(钢直浇布什和顶出针)。聚醚醚酮是一种高结晶度的工程塑料,导致其有利的性质。零件表明,开发高结晶度不可能在一个不能供热的钢工具,为什么必须钢模具预热至摄氏200 C。 目前甚至短裤分聚醚醚酮的一般要求Ensinger保证生产钢铁的工具。铝工具,加快了生产,是不可能出现的热传导过程甚至比钢和将很难维持成型鬼脸温度为200C的一个。 7.总结和工业意义 第一例聚醚醚酮的一般注塑软工具。 第一例成功的注塑聚醚醚酮的一般在不能供热的工具。 最大的已知的熔体温度用于SL成型(以前所使用的最高RMRG;270篊)。示范较低的工艺参数与SL模具有可能由于其热特性。 显示出一种可能的选择钢批量生产工具部分低聚醚醚酮的。参考文献1希尔顿, P.D & 雅各布斯, P.F., 2000, 快速模具: 技术和工业应用, (Marcel Dekker), ISBN 0-8247-8788-9. 2罗伯茨,s.d和Ilston,T.J. ,1998年,直接快速成型注塑工具,7th研讨会论文集,欧洲及快速原型制造,77th - 9th亚琛、德国,由坎贝尔,消除,457 - 470页。3印地安人的认知,1996年,近年来从Stereolithography快速模具,全国学术研讨会,2nd快速成形和模具研究、8th - 19th 11月、白金汉郡大学、英国、135 - 152页,ISBN:085298 2。4Stierlen,p . Dusel,k - h。 和Eyerer,p . 1997、材料快速模具技术,8th欧洲大会在RP&M。诺丁罕。英国。5Dusel,k - h。 1997材料快速模具技术、社会生产快速成形制造工程师会议,22nd - 24th四月,迪尔伯恩出版社,美国。6运气,洪志雄、Baraldi,美国,1995,下游技术比较功能与技术,快速模具与RP原型研讨会论文集,4th欧洲记者发布会上,13th - 15th六月,Belgriate、意大利、247 - 260页。7Schulthess a,Steinmann,b和霍夫曼,m .,1996年,CibatoolTM SL的环氧树脂一些新应用,1996年北美Stereolithography用户小组会议上,3月10 - 14,圣地牙哥,美国。8Eschl,j .,1997年,经验photopolymer插入注塑、欧洲人Stereolithography用户小组会议上,2nd - 5th 11月,意大利的佛罗伦萨。9道森,k .,1998年的影响,对最终产品的性能快速模具。学报北美用户Stereolithography小组会议上,1st - 5th三月,圣安东尼奥马刺队,美国。10Michaeli、韩长富,Brinkmann,s .和后,m .,1996年,怎样紧密零件RT模模具系列生产吗?,Kuntstoffe Plast欧洲,v86,n11,年11月,9 - 10页。11Damle、m、黄兆龙,王水,马洛依,麦卡锡,王水,1998,纤维取向的影响力学性能的部分和Stereolithography-Insert注塑成型部分,塑料工程师协会(SPE)年度技术会议(ANTEC美国亚特兰大,584 - 588页。12哈里斯,r . a .,Newlyn,h。 一个,狄更斯、p . 2002A.模具的选择设计变量直接Stereolithograph注塑模具模具,杂志工程制造、IMechE B部分学报216卷,没有B4 ISSN 0954 -4054。 499 - 505页。13哈里斯。R.A,Hopkinson。 氮、Newlyn。 H、海牙。R &狄更斯、点,2002b,层草案选择厚度和角度stereolithography注塑模具模具,国际杂志的生产研究,体积40卷,3、15th 2002年2月,第729 - 719页,ISSN 0020 - 7543。原文出处：HARRIS, R.A., HAGUE, R.J.M. and DICKENS, P.M., Thermal conditions in stereolithography injection mould tooling ，International Journal of Production Research Taylor & Francis ，2004，42(1) pp ，119 - 129 。图1.探头位置说明图 2.截面的观点插入热电图 3. 艾尔温为1赔断面轧件图 4. SL临时断面轧件为1赔图 5. 平均温度剖面美联及SL模具图 6.1st试验断面的工具图7. 部分来自于1st试验图8. 部分来自于2nd试验Thermal conditions in stereolithography injection mould tooling R. A. Harris*, R. J. M. Hague & P. M. Dickens Rapid Manufacturing Research Group Wolfson School of Mechanical & Manufacturing Engineering Loughborough University, UK * Corresponding author: R.A.Harrislboro.ac.uk 1. Abstract The use of stereolithography (SL) as a rapid tooling technique for injection moulding provides a low cost and quick alternative to hard tooling methods when producing a small quantity of parts. However, previous work has shown that different characteristics are developed by crystalline plastic parts produced from SL moulds and those produced from conventional tooling methods. Differing characteristics means that the parts are not truly the same as those that would be produced by hard tooling and highlights a disadvantage to SL tooling. Such differences are due to the cooling rate experienced by the part. Parts produced from SL moulds are cooled more slowly than those from metal tools as a result of the differing thermal conductivity of the mould material itself. This work concerned establishing the extent of the difference in the heat transfer characteristics. The different cooling rates were demonstrated by real-time data acquisition. The results illustrated the very different thermal history imparted on the moulding that are likely to be the cause of characteristical differences in the parts. The work then describes how the thermal conditions experienced in stereolithograph moulds can be used to an advantage. A case study details the use of SL moulds for the injection moulding of polyether-ether-ketone (PEEK) which has high process parameter demands. The results of the case study have shown that not only is the stereolithography rapid tooling method capable of producing a low volume of PEEK parts, but also under conditions that would not be possible using a metal mould. The thermal characteristics of stereolithography moulds allowed fully crystalline PEEK parts to be produced with the mould at room temperature; the equivalent steel mould would require a pre-moulding temperature of 200C and much higher injection pressures & speeds . Keywords: Stereolithography, Rapid Tooling, Injection Moulding, Heat Transfer, Polyetherether-ketone. 2. Background The term Rapid Prototyping (RP) refers to the production of a physical geometry by one of a group of processes. RP processes directly produce a geometry from data derived from a 3D representation (i.e. CAD - computer aided design). The processes are characterized by generating the geometry by an additive, layer-by-layer manufacturing sequence, which when initiated runs unattended. Stereolithography (SL) is one such RP process. SL is the most mature commercial RP process, its development began in the mid 1980s. SL represents one of the most geometrically accurate commercial RP processes with a minimum feature size of approximately 0.1mm possible. SL generates a solid object by selectively curing a photosensitive liquid resin by exposure to UV light provided by laser. The part is generated section-by-section on a platform which is contained within the bath of the liquid resin. The materials that can be used in the process are restricted to acrylic and epoxy resins. Resins of very different characteristics are available but they are all essentially variants of epoxy and acrylic (in this work epoxy is used). It has been shown that SL is capable of producing tooling cavities that can be used for the injection moulding of a limited number of parts in various polymers (1, 2, 3, 4, 5, 6, 7). The tooling cavities (inserts) generated by SL possess very different heat transfer characteristics as compared to traditional tooling materials for injection moulding: Thermal conductivity SL epoxy0.2W/m-KSteel50W/m-KAluminium200W/m-KThese differences in heat transfer properties have commonly been perceived as a weakness of the SL moulding process as they result in a slower cooling of the part and consequently longer production cycle times. It has also been shown that the heat transfer properties of SL moulds results in parts that demonstrate different characteristics to those produced from metal moulds. Crystalline polymers have been shown to exhibit the following characteristics when produced from SL epoxy moulds as compared to those from metal moulds: Greater strength & stiffness(8) Lower impact strength(9) Greater density(10) Greater shrinkage(11)Such differences relate to a higher level of crystallinity which is developed within the parts from SL moulds due to their slower rate of cooling. This slower rate of cooling is due to the difference in the thermal conductivities of the tooling materials. This work illustrates the differences in the rate of part cooling in SL and aluminium moulds by a real-time data acquisition set-up. The advantages to the thermal conditions experienced in SL moulds is later demonstrated in a case study. 3. Methodology 3.1 Tool Design The part and tool design used in the experiments were taken from earlier work in part shrinkage evaluation. The moulded specimen consisted of a bar shape with dimensions 12.7mm by 127mm, with a wall thickness of 3.2mm. This cavity was gated at one end, measuring 6.4mm in width and 3.2mm in depth. An open gate was utilised to ensure no areas of heat and pressure build-up, which SL moulds are vulnerable to. The tool did not incorporate an ejection system in order to ensure a singular rate of heat transfer within the mould cavity, i.e. the inclusion of a steel ejector pin in an epoxy mould would provide an area within the mould that conducted heat at a greater rate. The absence of an ejection system was no problem as the parts were easily removed by hand. The tool materials evaluated were SL epoxy and aluminium. Aluminium was chosen as suitable comparison metal tooling material as it is often utilised when producing metal tools in a short time (fast machining rates possible). Aluminium (AL) also represents a tool of highly contrasting heat transfer characteristics compared to SL epoxy. 3.2 Injection moulding The polymer used in the injection moulding was Nylon PA66, specifically Bergamid A70NAT produced by PolyOne. This was dried immediately prior to moulding. The injection moulding machine used was a Battenfeld 600/125 CDC model with a Unilog 4000 control unit. This machine consisted of a 60 tonne hydraulic clamping unit and a 125x35mm reciprocating screw injection unit. The defining injection moulding parameters were: The injection speed used was 100mm/second. The injection pressure was 150 bar. Upon mould filling a follow-up pressure of 150 bar was held for 1.5 seconds. A mould temperature of 23.5C prior to injection and temperature recording. A melt temperature of 270C. A cooling time of 40 seconds. 3.3 Temperature sensing In order to establish the heat transfer characteristics occurring in each of the moulds, the temperature was recorded throughout the moulding cycle by the insertion of PTFE insulated k-type thermocouples with a welded tip. The thermocouples were inserted in three positions in the moulding cavity. Two were distributed evenly along the length of the moving side and one in the centre of the length on the non-moving side of the mould. These positions are illustrated in figure 1. The tip of the thermocouple was situated such that it was located 0.5mm below the surface of the moulding face. The thermocouple was inserted from the rear of the mould insert through a 1mm drilled hole. The end point of the hole was created using a ball nosed cutter similar in profile to the welded tip of the thermocouple. This was created to ensure a good contact between the two surfaces without requiring any adhesives. It was thought that the use of any adhesives could create an inaccuracy in the recorded temperatures values due to the adhesive not having the same heat transfer characteristics as the mould material. Inserting the thermocouple firmly into the hole and securing with glue around the wire lengths enabled recordings to be taken without any signal disruption due to vibration from the injection moulding machine. The affixing of the thermocouples in the cavity inserts is illustrated in figure 2. The tool temperature recording system was calibrated in order to verify that the recorded value from the thermocouple was an accurate reflection of the temperature condition at the mould cavity surface. After insertion in the mould, a known temperature was applied to each of the probe positions on the mould cavity surface and a comparison of the recorded temperature from each probe and the actual mould cavity surface temperature was made in respect to their simultaneous values and their response to temperature change. In both cases (SL & AL mould) the difference between the temperatures measured by the thermocouple and the actual surface temperature was never greater than +/- 1oC. The temperature profiles experienced in each mould were acquired by a data acquisition set-up that monitored and recorded the temperatures over a period of time. The readings were taken from the three thermocouples in each mould, these readings were converted to digital signals and, using a developed software programme, then filtered and sampled at linear intervals to provide a temperature history profile of the moulding conditions. This set-up recorded the temperature profiles experienced during the production of one moulding over a ten minute period. Twenty mouldings were produced and the temperature profiles recorded. 4. Results & Discussion 4.1 Temperature profiles during one shot Examples of the thermal profiles experienced in the AL and SL moulds are shown in figure 3 & figure 4. The following observations can be made from the thermal history profiles: Each of the temperature profiles showed a consistent start temperature of 23.5oC. The temperature of the environment in which the injection moulding machine was situated was 18oC. The greater ambient temperature of the mould was caused by a combination of the closed cabinet (completely enclosed safety guarding) and heat from the machines hydraulic clamping unit where the oil was maintained at a constant temperature. Close observation of the peak temperatures in each case shows that slightly higher temperatures are experienced by the probes closest to the gate where material enters the mould. This is probably due to their slightly longer period of exposure to the hot polymer melt due to the manner in which the mould fills. The SL moulds demonstrate a sudden drop after their temperature peak, at 48-52 seconds. This was the time of mould opening when the heat in the mould suddenly finds another route to dissipate itself into the air. No such characteristic was displayed in the AL moulds as the temperature peaks after only 2.8 seconds and nearly all activity had ceased by 48-52 seconds .4.2 Average temperature profiles over twenty shots The similarity between the thermal history profiles from each shot (no greater than +/- 5%) allowed an average temperature profile to be generated for each mould type (AL & SL).The average temperature profile experienced in each mould type over 20 shots is shown in figure 5. The profiles shown figure 5 illustrate the vastly different temperature conditions experienced in the SL and AL moulds. The temperature activity in the AL moulds occurred in a very short period of time due to the materials high thermal conductivity. The temperature profile in the SL mould was more extreme and protracted, without external assistance (i.e. cooling by compressed air) the SL mould would take 15 minutes to return to its ambient temperature. 5. Case study 5.1 Background The work described was conducted as part of the European Union funded IMS RPD project. The project partly involved research into the use of Stereolithography (SL) moulds for producing prototype quantities of plastic parts by injection moulding. The project had successfully moulded different polymers in SL moulds in an order that represented a progression in their difficulty. The polymers in chronological order were polypropylene,acrylonitrile-butadiene-styrene, polyamide 66 & polyamide 66 with 30% glass content. The use of polyether-ether-ketone (PEEK) would represent a significant jump in this progression to a highly mould-aggressive material. PEEK is a highly crystalline engineering polymer with great temperature resistance, great hardness, high accuracy, environmental stability and low frictional properties. It is used in top-end plastic applications such as in medical and aerospace industries. PEEK also has extreme injection moulding processing requirements; a melt temperature of 400C, a mould temperature of approximately 200C & a typical injection pressure of around 800 bar. This particular section of work was conducted in conjunction between the Rapid Manufacturing Research Group (RMRG) of Loughborough University and the global plastic processors, Ensinger in Germany. 5.2 First Trials The first attempts at moulding PEEK in SL moulds utilised a simple mould geometry that had been used in previous experiments by the Author (12, 13). The mould consisted of a direct sprue which moulds around a central cylindrical core feature followed by a flange which the ejector pins act upon. A cross section of the mould is shown in figure 6. Two of these SL moulds successfully produced 15 PEEK parts each. The moulds were in a reasonable condition after moulding, although they exhibited wear at the point of material entry into the SL moulds. The process parameters used are shown below: Process parameters used in 1st trials Polymer meltMouldInjectionInjection speedtemperature (oC)temperature (oC)pressure (bar)(mm/sec)SL mould40023 (room temp)257Requirements in an equivalent 40020050050steel mould (approx) The parts themselves displayed very interesting characteristics. The part area in contact with the SL mould was grey, which indicated this area of the part was crystalline. The areas in contact with the steel sprue bush and ejector pins were brown, which indicated an amorphous region in the part. This is illustrated in figure 7. 5.3 Second Trials The IMS RPD project utilised real part designs as a demonstration of technology transfer. An impeller provided by the industrial partner Rotax-Bombardier had been produced in various injection moulding polymers using SL moulds. After the initial success in the 1st trials it was decided that attempts should be made to produce these impeller parts in PEEK. Two SL moulds successfully produced 10 PEEK parts each. The moulds suffered from wear at the first point of material entry into the mould and also at the 4 points of material entry into the cavity. Process parameters used in 2nd trials Polymer meltMouldInjectionInjection speedtemperature (oC)temperature (oC)pressure (bar)(mm/sec)SL mould40023 (room temp)3010Requirements in an equivalent 40020065070steel mould (approx) The parts again showed amorphous regions where the polymer came into contact with the steel areas of the mould cavity. These parts are shown in figure 8. 6. Discussion The results have shown that the thermal characteristics imposed by SL moulds, which are commonly viewed as a disadvantage of the process, may in some cases be advantageous and allow moulding in conditions that would be unobtainable in metal tooling. The success of the process and the characteristics of the part are due to the thermal properties of the mould. The great disparity in the thermal conditions experienced has been quantified by experimentation. The SL epoxy mould transfers heat away from the part much more slowly than the steel mould due to their different thermal conductivity. This allows for an unheated mould and lower process parameters to be used. This work illustrates the inherent heat transfer characteristics of SL moulds which enable their use in this injection moulding application, SL moulding would not be able to withstand the preheating and higher injection pressures and speeds that are required in equivalent metal tools. It is particularly interesting that the mouldings exhibit amorphous areas where the polymer comes in to contact with areas of high heat conduction (the steel sprue bush and ejector pins). PEEK is a plastic of high crystallinity, which results in its favourable properties. The parts demonstrate that the development of high crystallinity would not be possible in an unheated steel tool, this why steel tooling must be preheated to 200C. Presently even shorts runs of PEEK mouldings require Ensinger to produce a steel tool. Aluminium tools, which are faster to produce, are not a possibility as the heat conduction is even greater than steel and it would be very difficult to maintain the moulding faces at a temperature of 200C. 7. Conclusions & Industrial Significance First known injection moulding of PEEK in soft tools. First known successful injection moulding of PEEK in unheated tools. Greatest known melt temperature used in SL moulding (highest previously used by RMRG; 270篊). Demonstration of the lower process parameters that are possible with SL moulds due to their thermal characteristics. Demonstration of a possible alternative to steel tools for low volume production of PEEK parts at a greater speed and lower cost. References 1. Hilton, P.D & Jacobs, P.F., 2000, Rapid Tooling: Technologies and Industrial Applications, (Marcel Dekker), ISBN 0-8247-8788-9. 2.Roberts, S.D. & Ilston, T.J., 1998, Direct rapid prototyping injection moulding tools,Proceedings of 7th European Conference on Rapid Prototyping & Manufacturing, July 7th - 9th, Aachen, Germany, Ed. by Campbell, R.I., pp 457-470. 3. Jacobs, P.F., 1996, Recent Advances in
- 温馨提示:
1: 本站所有资源如无特殊说明，都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
2: 本站的文档不包含任何第三方提供的附件图纸等，如果需要附件，请联系上传者。文件的所有权益归上传用户所有。
3.本站RAR压缩包中若带图纸，网页内容里面会有图纸预览，若没有图纸预览就没有图纸。
4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
5. 人人文库网仅提供信息存储空间，仅对用户上传内容的表现方式做保护处理，对用户上传分享的文档内容本身不做任何修改或编辑，并不能对任何下载内容负责。
6. 下载文件中如有侵权或不适当内容，请与我们联系，我们立即纠正。
7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
人人文库网所有资源均是用户自行上传分享，仅供网友学习交流，未经上传用户书面授权，请勿作他用。
川公网安备: 51019002004831号